The present invention relates to a light emitting element drive device that drives a light emitting element, such as a light emitting diode (LED). Specifically, the light emitting element drive device performs pulse width modulation (PWM) dimming.
Japanese Patent Publication No. 2005-142137 discloses an LED lighting device. In the disclosed LED lighting device, a current flowing in an LED module is detected. The LED module is configured with a plurality of LEDs that are connected in series. Then, an operation of a direct current (DC) voltage conversion circuit is controlled so as to make the detected current a constant value (a target current value). In the circuit shown in FIG. 13 of Japanese Patent Publication No. 2005-142137, dimming of the LED module is performed by changing an ON-OFF ratio of a dimming switch element that is connected to the LED module in series. In the disclosed circuit, because a current flows in the LED module only in the case in which the dimming switch element is turned ON, the above control, i.e., the current flowing in the LED module becomes the target current value, is performed only when the dimming switch element is turned ON.
However, the above conventional technology has the following problems. Even though the above control (the current flowing in the LED module becomes the target current value) is performed immediately after the dimming switch element, which is connected to the LED module in series, is turned ON, it takes a certain period of time until the current actually reaches the target current value. Therefore, before the current reaches the target current value, a stable light output cannot be obtained.